Photographic desensitizing



Patented Oct. 4, 1938- UNITED STATES PATENT OFFICE PHOTOGRAPHIG nnsnmsmzmc No Drawing. Application October 7, 1936; Serial No. 104,442. In Germany October 11, 1935 17 Claims.

Our present invention relates to photographic de'sensitizing.

One of its objects is to provide a process of photographic desensitizing. Another object is the new desensitizers. Further objects will be seen from the detailed specification following hereafter.

It has been proposed to'use water-soluble derivatives of anthraquinone or phenanthrenequinone, particularly anthraquinone-carboxylic acids and anthraquin'one-sulfonic acids, for desensitiz- .ing light-sensitive, particularly pan-chromatic, silver halide emulsions. These water-soluble compounds, however, have not come into use because their desensitizing effect is comparatively small, and is considerably inferior to that of the known pinacryptol-green. Some of the said compounds are also open to the objection that they form precip tates in water containing lime compounds, and others that they are colored.

Both of these properties are undesirable in a desensitizer.

This invention is based on the observation that the taurides of anthraquinone-carboxylic acids 23 and sulfonic acids have a pronounced desensitizing capacity and are free from the foregoing objections. Their desensitizing effect exceeds considerably that of the hitherto known best desensitizers, namely pinacryptol-green. The 30 'taurides do not form sparingly soluble lime salts and are colorless. Owing to thecombination of these favorable properties, the taurides may be regarded as ideal descnsitizers. They' may be used either in a preliminary bath or as an addition to the developer. Where a preliminary bath is used its desensitizing effect may be considerably enhanced by addition of sodium-sulfite. correspondingly, when used in the developer their eifect is the stronger the more sodium- 0 sulfite the developer contains. Suitable compounds are for instance anthraquinone-l-sulfomethyl-tauride, anthraquinone 2 sulfomethyltauride, anthraquinone-sulfotauride, anthraquinone-2-chloro-3-sulfomethy1tauride, anthraqui- 45 none-2.6-disulfomethyltauride, anthraquinone-2-- carbonylmethyltauride and anthraquinone e 2 chloro-3-carbonylmethyltauride.

The following examples illustrate the invention: Example 1.--1 gram of the sodium-salt of an- 50 thraquinone-l-sulfo-methyltauride is dissolved in 1 litre of water and in this solution orthochromatic or panchromatic photographic layers are bathed for 2 minutes. Development may then follow, for example in a bright green light.

55 Ercample'2.--1 gram of the sodium salt of anthraquinone-2-sulfo-methyltauride is dissolved in 1 litre of water, together with 25 grams of anhydrous sodium sulflte. In this solution photographic layers are bathed for 2 minutes and may then be developed in a bright green light.

Ezcample 3.--Ortho-chromatic and panchromatic photographic layers are developed in one litre of a developer of the following composition:

Water litre 1 Metal (mono-methyl-p-aminophenol) grams" 8 Anhydrous sodium sulflte do 125 Anhydrous sodium carbonate do 5.8 Potassium bromide do 2.5 Sodium salt of anthraquinone-Z-sulfomethyltauride gram 0.5

The development may be first for 1 minute in the dark and then continued in a bright green or yellow light.

The simplest compounds of the class of substances to which the invention relates may be represented by the following formulae:

1. Anthraquinone-Z-sulfotauride 2. Anthraquinone-2-carbonyl tauride oo-mn-om-bm-som silver halide emulsions which comprises immersing said silver halide emulsion before development in an aqueous preliminary bath containing a tauride of a compound selected from the group consisting of anthraquinone carboxylic acids and anthraquinone sulionic acids and an alkali sulflte.

5. A process for desensitizing light sensitivesilver halide emulsions which comprises developing said silver halide emulsions in an aqueous solution of a developing agent and a tauride of a compound selected from the group consisting of anthraquinone carboxylic acids and anthraquinone sulionic acids.

6. A process for desensitizing light sensitive silver halide emulsions which comprises developing said silver halide emulsions in an aqueous solution of a developing agent and a tauride of a compound selected from the group consisting of anthraquinone carboxyiic acids and anthraquinone sulfonic acids and an alkali sulfite.

7. A process for desensitizing light sensitive silvemhalide emulsions which comprises immersing said silver halide emulsions in a bath being composed of 1000 cc. water and 1 gram of the sodium salt of the anthraquinone-l-sulfomethyltauride. v

8. A process for desensitizing light sensitive silver halide emulsions which comprises immersing said silver halide emulsions in a bath being composed of 1000 cc. water, 25 grams of anhydrous sodium sulfite and 1 gram of the sodium salt of the anthraquinone-2-su1fomethyltauride.

9. A process for desensitizing light sensitive silver halide emulsions which comprises developing said silver halide emulsions in a developer being composed of 1000 cc. of water, 8 grams of mono-methyl-p-aminophenol, 125 grams of anhydrous sodium sulfite, 5.8 grams of anhydrous sodium-carbonate, 2.5 grams of potassium bromide and 0.5 gram of the sodium salt of the anthraquinone-2-sulfomethyltauride.

10. As a desensitizer for light sensitive silver halide emulsions a tauride of a compound selected from the group consisting oi anthraquinone carboxylic acids and anthraquinone sulfonic acids in aqueous solution.

11. A bath for desensitizing light sensitive silver halide emulsions containing a tauride of a compound selected from the group consisting of anthraquinone carboxylic acids and anthraquinone sulfonic acids in aqueous solution.

12. A bath for desensitizing light sensitive silver halide emulsions containing a tauride of a compound selected from the group consisting of anthraquinone carboxylic acids and anthraquinone sulfonic acids and an alkali sulfite in aqueous solution.

13. A developer for developing light sensitive silver halide emulsion layers comprising an aqueous solution of a developing agent for silver halide emulsions and a tauride of a compound selected from the group consisting of anthraquinone carboxylic acids and anthraquinone sulfonic acids.

14. A developer for developing light sensitive silver halide emulsion layers comprising an aqueous solution of a developing agent for silver halide emulsions and a tauride of a compound selected from the group consisting of anthraquinone carboxylic acids and anthraquinone sulfonic acids and an alkali sulfite.

15. A bath for desensitizing silver halide emulsions being composed of 1000 cc. of water and 1 gram of the sodium salt of the anthraquinone-lsulfomethyltauride.

16. A bath for desensitlzing silver halide emulsions being composed of 1000 cc. of water, 25 grams of anhydrous sodium sulfite and 1 gram of the sodium salt of the anthraquinone-2-sulfome- KARL KUMETAT. SEBASTIAN GASSNERi 

